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Fat

Contrary to popular belief, fat is an essential nutrient with a host of important functions within the body. It is essential for supplying the body with omega 3 and omega 6 essential fatty acids, producing healthy cell membranes and maximising the absorption of fat-soluble vitamins and fat-soluble antioxidants (such as lycopene and beta-carotene). Fat is found in many foods and comes from both animal and vegetable sources.

Fat often receives bad press, but it is eating too much of certain types of fats and not enough of others which is detrimental, not fat per se. Fat is energy-dense, meaning it contains a lot of energy (kilojoules/calories) in a small quantity (37kJ/g), making it easy to eat more than we need.

Different types of fat

The main types of fat are saturated, polyunsaturated, monounsaturated and trans fats.

Saturated fat increases total cholesterol by increasing the ‘bad’ LDL cholesterol, so it should be eaten in the smallest amounts. We should aim to reduce saturated fats in the foods we eat, and where fat is used, choose monounsaturated and polyunsaturated fats. Sources of saturated fat: Butter, cheese, meat fat, meat products (sausages, hamburgers), full-fat milk and yoghurt, pies, pastries, biscuits, cakes, lard, dripping, hard margarines and baking fats, coconut and palm oil.

Polyunsaturated fats can be further divided into omega–3 and omega–6. Omega-3 fats have a positive impact on heart health and an important role in brain and eye function. Omega-6 fats are necessary for growth and the synthesis of hormone type compounds. Sources of polyunsaturated fats: long chain Omega-3 polyunsaturated: Oily fish (salmon, mackerel, herring, trout), Alpha linolenic acid from walnuts, lean red meat, canola oil, soybean, flax seed, and their oils. Omega-6 polyunsaturated: sunflower seeds, wheat germ, sesame, walnuts, soybean, corn and their oils. Certain margarines.

Trans fats are formed mainly during the process of hydrogenation of edible oils to make solid fats used in shortenings and margarines. Trace amounts can be produced in the heating and frying of oils at high temperatures. They are also found naturally in beef, mutton, lamb and dairy fat. Sources of trans fat: some margarines, shortenings, biscuits, baked goods.

Like saturated fat, but thought to be even more harmful, manufactured trans fats increase ‘bad’ LDL cholesterol in our blood, a risk factor for heart disease. In addition, trans fats may also decrease levels of the ‘good’ HDL cholesterol, making the effect of trans fat worse than saturated fat. Currently in New Zealand, we eat well below the recommended levels of trans fat suggested by the World Health Organisation (WHO), which is well below many other countries (mainly due to the low levels of trans fats in our margarines, compared with the US and UK). However, we are eating too much saturated fat, and need to try to reduce this as a population.

NZNF White Paper - Dietary Fats & Oils

Dietary fats play an important role as a source of energy, as structural components and as carriers of other dietary components including fat-soluble vitamins. However, the role of different dietary fats and oils in human nutrition is one of the most complex and controversial areas of investigations in nutrition science. Experts agree evidence does not suggest total fat intake has significant effects on risk of coronary heart disease (CHD) or cancers. The primary concern and importance is the potential relationship between total dietary fats and body weight, as overweight and obesity are risk factors for both cardiovascular disease (CVD) and cancer. As it is currently not possible to determine at a probable or convincing level the causal relationship of excess percent of energy (%E) from fat and unhealthy weight gain, maintaining current World Health Organization (WHO) recommendations (30-35%E total fat) seems prudent.

Tips

All fat contains the same number of kilojoules/calories, regardless of which type of fat it contains. So use fats and oils sparingly if you are watching your weight.

Use low-fat cooking methods such as grilling, baking and microwaving instead of frying to reduce the amount of fat and oil.

Compare labels to choose lower-fat products – a food is considered low in fat if the total fat level less than 10g/100g (or 10%). Choose foods that have a low proportion of saturated fat compared to total fat – the rest will be made up of the healthier mono and polyunsaturated fats.

Easy ways to reduce the amount of saturated fat you eat is by choosing low-fat milk or yoghurt and lean cuts of meat, removing any visible fat from meat and skin from chicken, and choosing margarine and vegetable oils (such as olive and canola oils or spreads) rather than butter.

Some oils break down when they are cooked at high temperatures. For frying, use canola, sesame, peanut or rice bran oils. Olive oils are best on salads and for low-temperature cooking.